The present invention relates generally to method for manufacturing a cover for a connector bar and the cover, and more specifically, to a method for quickly manufacturing the cover for a connector bar separate and apart from the connector bar that is used in aboveground pedestals.
Aboveground power distribution pedestal box can be installed at intervals along a utility easement, such as in residential communities. Often, main power cables are run from one pedestal box to another, with the power cables terminating and connector bars located in each of the boxes. Connector bars are typically rectangular blocks of metals having openings for the main power line conductors or cable, and additional openings for distribution cable to residence or other dwellings, or to other utilities. Screws or other connection mechanisms are provided to secure the conductors or cables mechanically and electrically to the connector bar. Typically, each pedestal box contains three connector blocks since a three-wire residential distribution system is commonly used in residential communities.
It is often required that a connector bar be insulated, covered or encapsulated in a nonconductive material to prevent several problems. Since the pedestal boxes are outdoors, a connector bar preferably needs to be insulated from adverse weather, such as rain or snow, so that the power system does not fail due to an electrical short in the system. Additionally, it is also advantageous to insulate a connector bar and its associated wires from other connector bars and wires in the pedestal box. Electrical isolation of a connector bar reduces the possibility of cables, wire, or other connection means or the connector boxes from coming into electrical contact with each other and shorting out the power supply system. Furthermore, while a pedestal box is almost always covered and locked to prevent unauthorized entry, it is possible at times for individuals to come into contact with a connector bar, either intentionally or accidentally. Therefore, it is preferable and desired to provide a insulating cover for a connector bar to minimize the potential for electric shock.
Traditionally, there has been a plastic (e.g., PVC) insulated coating surrounding and insulating a metal connector bar. This plastic coating has been formed around and is fused or sealed to the connector bar. In order to properly coat the connector bar and form the ports, the connector bar, with its opening, must first be prepared. Preparation steps include inserting plug inserts into the screw and wire openings that plug or fill the hole, and extend outwardly away from the connector bar. In some applications, there are at least two screw openings and two wire openings in each connector bar that need to be filled or plugged with insert plugs. Thereafter, the connector bar is pre-heated and then is coated with a polymer material, usually by dipping the connector bar into the polymer material or solution for a predetermined time period. Next, the covered bar is cured (e.g., either by heat or other means) for a predetermined period of time so that the polymer material sufficiently hardens to form the cover and seizes or otherwise adheres to the connector bar""s outer surface.
After the polymer is sufficiently cured, the ends or tips of the wire port(s)and screw port(s), which were generally formed around the plug insert are manually trimmed, or otherwise removed, which forms openings in the ports. Next, plug inserts are manually removed from the connector bar through the recently-formed openings.
However, the present method is labor intensive, which adds to the time and complexity of the manufacturing process, and is not entirely satisfactory. Moreover, since the plug inserts are formed to accommodate the variations in the openings size of connector, they must be adapted to be insertable into the smallest possible opening in the connector bar. As such, gaps are sometimes provided between the plug inserts and the openings when they do not fit securely, and the polymer solution can leak into these gaps during the cover forming process. As the cover cures, the leakage forms burr and other irregularities in the opening, which must be trimmed or otherwise removed, typically by hand, so that cables and attachment means (e.g., screws or bolts) can each be properly inserted into their opening without interference.
In addition, when the cover is formed directly on and fused to the connector bar, sometimes the process of curing or heating the polymer solution burns or otherwise discolors the connector bar, which can be unsightly and present a xe2x80x9cdirtyxe2x80x9d appearance. Also, the repeated heating of a connector bar in the cover forming process causes unnecessary wear on the connector bar.
As can be appreciated, currently available plastic-covered connector bars for use in pedestal boxes have a number of shortcomings that contribute to the complexity and questionable quality of manufacturing. There exists a continuing need in the industry for a method for manufacturing covers for connector bars which can eliminate the wear and tear on the bar through the coating process. It is also desirable to provide an improved method of manufacture that eliminates many of the labor intensive steps currently involved in the manufacture of a cover for a connector bar. Furthermore, a need exists in the industry for a cover for a connector bar that is a separate structure and that is not adhered to the connector bar""s outer surface.
It is an object of the present invention to provide a method of manufacture and cover for a connector bar that addresses and overcomes the above-mentioned problems and shortcoming in the industry.
It is another object of the present invention to provide a method of manufacture and cover for a connector bar that eliminates discoloration on the connector bar.
Yet another object of the present invention is to provide a method of manufacture and the cover for a connector bar that eliminates wear and tear on the connector bar in the cover manufacturing process.
Still another object of the present invention is to provide a method of manufacture and cover for a connector bar that reduces the need for labor intensive post manufacturing finishing work.
Another object of the present invention is to provide a cover for a connector that is durable and can be used in outdoor pedestal boxes.
An object of the present invention is to provide a method of manufacture and cover for a connector bar that reduces the need for labor intensive pre-manufacture preparation work.
A further object of the present invention is to provide a cover that is relatively moisture resistant.
Additional objects, advantages and other features of the invention will be set forth and will become apparent to those skilled in the art upon examination of the following, or may be learned with practice of the invention.
To achieve the foregoing and other objects, and in accordance with the purposes herein, the present invention comprises a method for manufacturing a cover for a connector bar that comprises providing a mold having a substantially rectangular shaped block having a first surface, and a second surface adjacent the first surface. Both the first and second surfaces each have at least one generally cylindrically shaped projection extending outwardly away from the surface. The mold can have at least one generally L-shaped aperture extending in the block, with each aperture terminating with an opening in each of the surfaces.
The cover is formed around the mold from the liquid polymer or plastic solution or material, such as a polyvinyl chloride (PVC) plastisol material. Prior to forming the cover, the outer surface of the mold can be treated with a releasing agent Suitable releasing agents include water based agents (e.g., silicone), grease based, wax based, or others. The mold can be pre-heated before dipping the mold in a polymer, solution or material. Pre-heating the mold can involve heating the mold at a temperature from about 300xc2x0 to about 700xc2x0 F. (148xc2x0 to 371xc2x0 C.), and for a period of time from about 10 to about 40 minutes.
To form the cover, the mold is next slowly dipped into a polymer solution, and can be allowed to dwell in the solution for a period of time from about 10 to about 300 seconds. The mold can be withdrawn from the polymer solution at a rate from about 2 to about 8 inches (5 cm to 20.3 cm) per minute. The resulting cover can have a wall thickness from about 0.060 to about 0.250 inches (0.15 cm to 0.64 cm).
Next, the cover is cured, and such process can be assisted by heating the plastic cover, at a temperature from about 250xc2x0 to about 500xc2x0 F. (121 to 260xc2x0 C.) for a period of time from about 6 to about 20 minutes.
After the cover is formed around the mold, it is removed from within the cover, preferably though an opening in the cover, while the cover is preferably at a temperature from about 125 and 400xc2x0 F. (51 to 204xc2x0 C.) to facilitate removal of the mold through the narrow slit opening. To assist in removing the mold from within the cover, air under pressure can be blown into the opening.
After the mold is removed from the cover, a connector bar can be inserted through the opening into the cover""s cavity while the cover is at a temperature from about 125xc2x0 to about 300xc2x0 F. (51xc2x0 to 148xc2x0 C.). Optionally, the opening can be closed or otherwise sealed after the connector bar has been inserted. One suitable technique includes radio frequency welding.
The cover for use with a connector bar of the present invention includes a body portion that is preferably a substantially rectangular shape and is formed of a polymer material such as a PVC plastisol compound. The body includes a first surface, and a second surface being oriented substantially normal to the first surface. The body portion can have a wall thickness from about 0.060 to about 0.250 inches (0.15 cm to 0.64 cm), and further includes a generally rectangular shaped cavity within. At least one projection extends away from both the first and second surfaces, and each is integrally formed with the body and has an aperture extending to the cavity.
The cover can also include a third surface being oriented generally normal to the second surface and oppositely disposed from the first surface. An opening, such as a narrow slit, is provided along the third surface. In a preferred embodiment, fin projection can be also provided that extends away from the third surface, and includes a narrow slit opening along its distal edge.